Using firebug if I replace the background-image url to url("/bo/rfRes/dsBtnGrad.png.faces?v=4.0.0.Final&db=eAFjZJBjZDBiZBBh!P!p-3!G!2mthxiYADggBv8_&ln=org.richfaces.images") then this button also become blue in color and things are fine.

Need help to understand why its getting overridden and how to fix it in a proper and optimal way.